Facsimile recording paper



United States Patent FACSIMILE RECORDING PAPER Arthur H. Mones, Brooklyn, N. Y., assignor to Faximile, Inc., New York, N. Y., a corporation of Delaware No Drawing. Application August 27, 1956 Serial No. 606,216

5 Claims. (Cl. 204-2) is impregnated with an electrolytic solution containing a marking compound. This compound is capable of reacting with ions supplied by the anode to form a colored mark wherever the anode contacts the paper.

Recording paper employed for facsimile communication purposes must meet certain important requirements. The paper must have the ability to produce marks having a density which is a function (preferably linear) of the current passed through the paper. The paper must remain active and resist discoloration when stored for extended periods. Recording marks should be stable when the paper is exposed to ambient conditions of light and air. The active ingredients in the impregnant of the paper must avoid discoloration of or transferring to adjacent sheets of marked or unmarked paper of the same or dilferent type. These requirements, with others,

are fully met by the electro-sensitive paper with which the present invention is concerned.

The invention has as a principal objective, the provision of an electrolytic recording paper impregnated with solution containing salicylaldoxime as a marking agent. A further objective is to provide an electrolytically markable recording medium including a high wet-strength porous support impregnated with an aqueous solution of an electrolyte and salicylaldoxime.

A further objective is to provide an electrolytically markable recording medium including a high wet-strength porous paper support impregnated with an aqueous solution of an electrolyte such as potassium nitrate and a sufiicient quantity of salicylaldoxime to provide a deep brown mark when an electric current is passed through the paper via a suitable anode and cathode. A further object is to provide a solution for impregnating a porous support to obtain an electrolytically markable recording medium, said solution containing an electrolyte and salicylaldoxime.

Other and further objects and advantages of the invention will become apparent from the following detailed description.

Recording paper impregnated with an aqueous solution of salicylaldoxime and an electrolyte is marked by electrolytic deposits of metal cations in the paper. The cations are obtained from the metal anode which is one of the electrodes employed to apply the marking current to the paper. The cations react with the salicylaldoxime to form a complexion which ranges in color from light to deep brown depending on the density of the applied current.

The salicylaldoxime which has a rather limited solubility is dissolved with the electrolyte in the water. White porous paper stock having a high wet-strength is 'immersed in the solution until the moisture content ranges from 35% to 45% by weight of the impregnated paper. The paper may now be disposed between a pair of electrodes. The electrodes should be resistant to corrosion by the moist impregnant. If an electric potential is applied to the electrodes the paper will be marked electrically. Brown marks of various degrees of density will be obtained with certain anodes depending upon the density of the current passing through the paper. Marks of different colors may be obtained by the use of anodes.

containing silver, iron, copper, nickel, stainless steel, chromium alloys, and other metals. The most satisfying brown marks which provide a goodcontrast against the white= background of the unmarked paper are made with a metal anode made of stainless steel containing chromium to some extent, or with a pure chromium anode.

In the above formulation, the quantity of salicylaldoxime may be varied from a minimum at about 25 grams up to its limit of solubility in the water. The lesser concentrations of salicylaldoxime result in less dense recorded marks. Concentrations of salicylaldoxime greater than 50 grams per 4 liters of water do not produce materially darker marks.

When using the above formulation, the recording paper should contain about 2.5 cubic centimeters of impregnant per square foot of paper. The impregnated paper will weigh about 6.5 grams per square foot. The paper will contain in each square foot about 2.20 grams of Water, 0.25 gram of electrolyte, and 0.03 gram of salicylaldoxime. The paper weighs about 4 grams. Thus, the content of the recording medium is approximately as follows:

The approximate proportions by weight of the contents of the impregnant in the paper are thus:

Percent Water 89 Electrolyte 10 Salicylaldoxime 1 Total If the minimum quantity of 25 grams of salicylaldoxime are used in the above formulation, the approximate proportions by weight of the recording medium will be:

Percent Paper 61.65 Water 34.08 Electrolyte 4.02 Marking compound 0.25

Total Patented Dec. 16,

pecans and the approximate proportions by weight of the con- Percent Water 89.4

Electrolyte 10.1 ewa e? Total 100.0

The purpose of the electrolyte is to render the impregnated paper electroconducti've. Sufficient electrolyte should'be usedso that thepaper'pass e's about 100 milliampercs' of" recording current at maximum applied voltage (30 to70 volts), in a marking 'area of about .01 of an inch The optimum resistance will be about 500 It was discovered that marks may be obtained having a uniformtonal "range from White through sepia to deep brown, even when very low marking currents are used. The'use of. externally applied heat "to' fix' or intensify th'e'recorded mark 'is'not required for recording paper containing salicylaldoxime asthe marking compound.

'"The'half-tone' recording characteristic of the impregnated paper is indicated by the following table in which marking current versus optical density and percent light reflectance is listed. Optical density is a measure of the amount 'of incident white light absorption. Optical density (O. D..') is related to light reflectance as follows:

100 percent. reflectance The data listed, was obtained by measurements of recorded marks made on paper impregnated with a formulation as stated above. The paper was marked in a facsimile recorder of the type described in patent to I. V. L. Hogan, No. 2,575,959, at 90 lines (of 8 inch length), per minute. In this recorder a linear anode is disposed to intersect a rotating helical cathode with the recording paper being advanced between the electrodes at uniform speed. The recorded marks were made with O. D.=log

It was noted as the data in thetable indicates, that as the recordingcurrent was increased, the optical density of,the r ecorded marks increased almost logarithmically. It. is a known physical phenomenon that, to the human ye a uniform ati hmiq hanse n p i a density ppears as' auniform linear change, thus as the marking currenfch'anges linearly the marks in this paper seem to: vary linearly in depth of color,

Other 'ox'ime's' which areknown reagents for producing complex cations as insoluble colored precipitates were tested for 'efiectiyeness as marking compounds in the recorder above mentioned. The impregnants were formulated'and"the papers were impregnated as described in the example above. The papers were marked with silver, copper, nickel, chromium, stainless steel, and chromium alloy anodes. A stainlesssteelcathode was used. Poor low density yellow and brown marks wereobtained with 5 nitro-sali'cylaldoxime and 5 l chloro salicylaldoxime. Th'e'best marks'a'sto uni'formity of color, density of cologfand stability were produced at low marking currents and voltages in papers containing only salicylaldoxime as the marking compound with metal anodes of stainless steel containing chromium and with pure chromium anodes. The particular metal used as the cathode is not important in so far as the chemical reaction involved in marking is concerned. Stainless steel cathodes were used with satisfactory results. The cathode material should be non-corrosive in the presence of water solutions contained in the paper and of water vapor released from the paper. The salicylaldoxime employed as the markingcompound in the present invention has a melting point of 57 C.59 C. It has a molecular weight of about 137.13 and its chemical formula is Various other electrolytes may be used instead of potassium nitrate to render the paper electrosensitive. Materials such as sodium chloride, ammonium nitrate, and the like may be used provided that the electrolyte material does not reactadve rsely with the marking compound and the electrodes.

The use of high wet-strength paper is important so that the paper may be marked at high speed while in a moist condition. A suitable paper of this type will be one containing melamine resins or the like permeating the fibrous structure of the paper. It is important that the resin be of such nature that it does not react with the impregnant to adversely affect the stability thereof or interfere with the marking process.

What is claimed is:

1. An electrically markable recording medium comprising a porous paper support having a high wet-strength impregnated with a solution containing salicylaldoxime as a marking compound, said solution containing substantially by relative weight:

Parts Salicylaldoxime 50 Electrolyte 400 Water 4000 Percent Paper 61.5 Water 34.0 Electrolyte 4.0 Marking compound 0.5

3. A recording medium adapted for being marked. elec; trolytically between a cathode and an anodejcontaining.

iron, comprising a white, porous paper sheet having 'a' high wet strength, said paper being'impregnated with a solution consisting essentially of an electrolyte and a marking compound, said compound being composed substantially entirely of salicylaldoxime, said solutionbeing capable of reacting with the anode to form marks of a color ranging from whiteto deep brown when varying electric currents are passedthrough thepaper. between the anode and the cathode.

4. An electrically markable recording medium comprisinga porous paper support having a high wet-strength, impregnated with an aqueous solution consisting essentially of an electrolyte, andfa sufiicient quantity ofa marking compound to provide a deep brown mark when an electric current is applied to the paper via a pair of electrodes consisting of an anode and a cathode, said anode being composed of a metal, said compound being.

comprising a porous paper support impregnated with an aqueous solution consisting essentially of an electrolyte and a marking compound composed substantially entirely of salicylaldoxime, the salicylaldoxime being present in at least 0.5% by weight of the solution.

References Cited in the file of this patent 

3. A RECORDING MEDIUM ADAPTED FOR BEING MARKED ELECTROLYTICALLY BETWEEN A CATHODE AND AN ANODE CONTAINING IRON, COMPRISING A WHITE, POROUS PAPER SHEET HAVING A HIGH WET STRENGTH, SAID PAPER BEING IMPREGNATED WITH A SOLUTION CONSISTING ESSENTIALLY OF AN ELECTROLYTE AND A MARKING COMPOUND, SAID COMPOUND BEING COMPOSED SUBCAPABLE OF REACTING WITH THE ANODE TO FORM MARKS OF A COLOR RANGING FROM WHITE TO DEEP BROWN WHEN VARYING ELECTRIC CURRENTS ARE PASSED THROUGH THE PAPER BETWEEN THE ANODE AND THE CATHODE. 